In our industrialized society it is not unusual to find multiple diverse instances wherein larger molecule liquids have been mixed with water. For example, bilge water typically comprises a mixture of petroleum oil with water, as does typical liquid waste collections from automotive repair and wash facilities, machine shops, metal stamping plants, and typically any number of industrial or repair facilities wherein liquids such as oils and water are, or can be, commingled in use or collection.
With the increased awareness of society for the environment, there has been an increasing need for means to separate such larger molecule liquids and water mixtures so that clean water can be returned to the environment while the larger molecule liquids can be recovered and recycled for the further use and benefit of mankind. Federal, state and local governments, in response to this increased awareness of society have promulgated and instituted new laws concerning the handling and disposal of such mixtures, particularly oil/water mixtures, such that it has become increasingly economically desirable to separate out as much water as possible from such mixtures conveniently at the site of commingling, to reduce the volume of liquid to be otherwise collected for recycle or disposal off site. Thus, there is an increasing need for a convenient, mobile device which will effectively and economically separate water from larger molecule liquids, particularly petroleum oils, to provide a reduced volume for collection, recycle and disposal at remote sites.
One device which has been proposed and is generally commercially available for the separation of such mixtures is the ultrafiltration device. In a typical ultrafiltration device a fluid containing mixture, such as oils with water is directed, under typically low pressure, to an ultra-filtration membrane. The ultra-filtration membrane comprises microscopic hydrophilic pores which will allow water to pass through the membrane but resist the passage of the oil molecules. Such selective activity is a function of the membrane, achieved through a combination of membrane characteristics including pore size, liquid contact angle and liquid surface tension. The membrane is typically arranged in a cross flow configuration wherein a feed from a water/oil mixture flows across the ultrafiltration membrane in such manner that the oil component of the mixture does not flow through the membrane but a portion of the water in the mixture will permeate the membrane at a low but acceptable pass-through rate. Thus, water flowing through the membrane comprises essentially no oil and can be recovered or wasted, in many instances without further treatment, while the treated mixture which does not permeate the membrane has an increased oil to water ratio. Typically the treated oil mixture, having an increased oil to water ratio, is returned to the feed mixture and is continually recycled in mixture with the feed mixture until the amount of water in the water/oil feed mixture has been significantly reduced.
Ultrafiltration devices of the type above described have typically been cumbersome units that require costly tending by the operator during the separation process to avoid harm to the membranes. Generally such prior art devices require extensive and complex disassembly procedures for routine cleaning and/or maintenance and as a result such units have not enjoyed a level of commercial success that might otherwise be expected. Such devices of the prior art also typically require about 24 hours or more to separate enough water from a 55 gallon container containing a typical 90:10 (water:oil) mixture to achieve a significantly concentrated typical 50:50 (water:oil) mixture while attaining an essentially oil free water waste containing less than about 50 ppm of oil.
It is an object of the instant invention to provide a mobile ultrafiltration device, capable of separating water from larger molecule liquids such as oils, to attain an essentially oil free water waste containing less than about 50 ppm of water, that is convenient to operate, is simplified in disassembly and internally protected from harm to costly membranes. These and other objects will become apparent from the following description of the invention.